Axial piston machine

ABSTRACT

A housing defines an elongated interior chamber bounded by an inner circumferential wall surface and having a longitudinal axis. A cylinder block is mounted in the chamber for rotation and has two axial ends and a plurality of open-ended passages paralleling the axis. A tilt plate is arranged in the chamber adjacent one end of the block and has a surface inclined to the axis and facing this one end, with a plurality of pistons being respectively reciprocably received in the passages and each having a free end-portion which bears upon the inclined surface of the tilt plate to slide thereon during rotation of the cylinder block. A stationary valve plate is mounted in the chamber and slide in contact with the outer end of the block and has a circumferential edge face facing the inner wall surface and a plurality of apertures adapted for registry with the bores of the cylinder block. At least one circumferential recess provided in the edge face extends inwardly towards but short of the aforementioned apertures.

United States Patent Reichel et al.

[ 1 Sept. 19, 1972 [54] AXIAL PISTON MACHINE [72] Inventors: Eckehard Re1chel,w Gerlingen;

Gustav Zellbeck, Esslingen-l-legensberg, both of Germany [73] Assignee: Robert Bosch Gmbl-l, Stuttgart, Germany- [22] Filed: Jan. 4, 1971 211 App]. No.: 103,444

[30] Foreign Application Priority Data Jan. 10, 1970 Germany ..P 70 00 688.1

7/1970 Espig et al. ..91/499 Primary Examiner-Edgar W. Geoghegan Assistant Examiner-A. M. Zupcic Attorney-Michael S. Striker [57] ABSTRACT A housing defines an elongated interior chamber bounded by an inner circumferential wall surface and having a longitudinal axis. A cylinder block is mounted in the chamber for rotation and has two axial ends and a plurality of open-ended passages paralleling the axis. A tilt plate is arranged in the chamber adjacent one end of the block and has a surface inclined to the axis and facing this one end, with a-plurality of pistons being respectively reciprocably received in the passages and each having a free end-portion which bears upon the inclined surface of the tilt plate to slide thereon during rotation of the cylinder block. A stationary valve plate is mounted in the chamber and slide in contact'with the outer end of the block and has a circumferential edge face facing the inner wall surface and a plurality of apertures adapted for registry with the bores of the cylinder block. At least one circumferential recess provided in the edge face extends inwardly towards but short of the aforementioned apertures.

10 Claims, 3 Drawing Figures 1 AXIAL PISTON MACHINE BACKGROUND OF THE INVENTION The present invention relates generally to an axial piston machine, and more particularly to an axial piston machine with a rotating cylinder block.

Axial piston machines are of course already known. Thus, German Pat. No. 1,243,020 teaches an axial piston machine having a rotating cylinder block with which a cylindrical component is made fast at the side which faces the valve plate surface which is provided on a stationary housing component, and in which inlet and outlet means are provided for pressure medium. The cylinder block bears with the associated cylindrical component upon a roller bearing in such a manner that a narrow gap exists between this component and the adjacent valve plate surface.

The circumferential edge face of the cylindrical component which is fast with the cylinder block is formed with a radially extending annular groove whose purpose is to permit the component to become deformed in axial direction at rising operating pressure in such a manner that the width of the aforementioned gap becomes smaller and leak oil losses are kept to an acceptable value. On the other hand, this measure also prevents a seizing of the relatively movable constituent components of the device.

This prior art construction has the disadvantage that the manner in which the cylinder block must be journaled is rather complicated and therefore expensive, and that the screwthreaded connection which is the solution taught in the aforementioned patentbetween the cylindrical component and the cylinder block requires additional operating steps which of course further increases the expenses involved.

SUMMARY OF THE INVENTION It is, accordingly, an object of the present invention to avoid the aforementioned disadvantages.

More particularly it is an object of the present invention to provide an axial piston machine which is simpler than what is known in the art but which is at least as reliable as the prior-art constructions, and actually more In pursuance of the above objects, and others which will become apparent hereafter, one feature of the invention resides in an axial piston machine which, briefly stated, comprises a housing defining an elongated interior chamber having a longitudinal axis and an inner circumferential wall surface. A cylinder block is mounted for rotation in this chamber and has two axial ends and a plurality of open-ended passages at least substantially paralleling the axis of the housing chamber. A tilt plate is provided in the chamber adjacent one end of the block and has a surface which is inclined to the axis and which faces this one end. A plurality of pistons is respectively reciprocably received in the passages and each has a free end portion bearing upon the surface of the tilt plate and being slidable thereon during rotation of the cylinder block. A stationary valve plate is mounted in the chamber in sliding contact with the other end of the block and has a circumferential edge face which faces the wall surface bounding the chamber and a plurality of apertures adapted for registry with the bores of the rotating cylinder block. At least one circumferential recess is provided in the edge face of the valve plate and extends inwardly towards but short of these apertures.

With this construction according to the present invention an axial piston machine is obtained which is considerably simplified over what is known from the prior art but which nevertheless avoids the disadvantages of the prior art mentioned above.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal section through an axial piston machine according to the present invention;

FIG. 2 is a fragmentary axial section through a valve plate such as used in FIG. 1, but of a different embodiment; and

FIG. 3 is a view similar to FIG. 2 but of still another embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing now firstly the embodiment illustrated in FIG. 1 it will be seen that reference numeral 1 identifies a cylindrical housing which is provided at the dry side thereof with a cover enclosing it. The cover is provided in turn with a journal 3 for a drive shaft 4, and also with an inclined surface 5 on which a tilt plate 7 of annular configuration is supported via the intermediary of rollers 6. The surface 7a of the tilt plate 7 is inclined to the longitudinal axis of the chamber defined in the cylindrical housing 1 and against this surface abut the rounded ends of pistons 8 which are reciprocably accommodated in bores 9 of a cylinder block 10 of generally cylindrical configuration.

As shown, the cylinder block 10 is rotated by the drive shaft 4 via a splined or toothed connection 1 l and pressed against a valve plate 12 which is non-rotatably mounted in the housing 11, for which purpose a non-illustrated retaining pin or the like may be provided. The valve plate 12 in turn abuts against a cover 13 closing the end of the housing opposite the cover 2 (that is the end which in FIG. 1 is the uppermost one) and in which a further journal 14 for the drive shaft 4 is provided. The drawing shows that the drive shaft passes through the rotating cylinder block 10 axially and centrally thereof.

The valve plate 12 is provided with several apertures 15 which cooperate with the bores 9 in the cylinder block 10. The opposite axial end faces of the valve plate 12 are provided with small spacing from the apertures 15 with annular grooves 16, 17, 18 and 19 between which sealing ribs 20, 21, 22 and 23 remain which circumferentially surround the apertures 15 radially outwardly thereof. The outer circumferential edge face of the valve plate 12 is provided with a circumferential recess or annular groove 24 the flanks or side walls of which in the embodiment of FIG. I extend in parallelism with one another. The groove 24 extends inwardly from the edge face 12a towards but short of the apertures 15.

An inlet opening 25 and an outlet opening 26 are both provided in the cover 13 and communicate in known manner with substantially kidney-shaped openings which in turn communicate with the apertures 15.

When the axial piston machine illustrated in FIG. 1 is operated, the valve plate 12 can become so deformed as. a result of expansion due to heating and also as a result of pressures acting upon it, that the gap between the rotating cylinder block and the stationary valve plate 12 becomes sometimes rather large, which would result in an increase of the leak or losses. This is true of course of all axial piston machines. The invention as disclosed in FIG. 1, however, avoidsthis difficulty by the provision of the annular groove 24 because stresses which occur during operation of the axial piston machine are relieved and the contact face of the valve plate 12, that is the face engaging the adjacent axial end face of the rotating cylinder block 10, will remain planar instead of becoming deformed, and will thus have optimum surface-to-surface contact with the associated end face of the cylinder block 10. This also significantly reduces the wear at the contacting surfaces of the valve plate 12 and the cylinder block 10, and thus prolongs the useful life of the axial piston machine.

In the embodiment of FIG. 2 we have illustrated the the cylinder plate 12', which here is shown fragmentarily, may also be provided with. two grooves 27 instead of the single groove 24 in its outer circumferential surface, and that these grooves may have side walls or flanks which converge in direction towards one another inwardly of the circumferential edge face. It is pointed out that instead of two of the grooves 27, a single groove could also be provided.

Similarly, in FIG. 3 we have shown that the valve plate which is here identified with reference numeral 12'', may also have two grooves in its outer circumferential surface of which one is identified with reference numeral 24 and corresponds in its cross-sectional configuration to the groove shown in FIG. 1,

whereas the other is identified with reference numeral" 27 and corresponds in its cross-sectional configuration to those shown in FIG. 2. Of course, the axial location of the grooves 24 and 27 in FIG. 3 could be reversed, that is the groove 24 could be uppermost (as seen with respect to the top of FIG. 3) and the groove 27 could be beneath it.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in an axial piston machine, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and an eo ui alenc ofth 0110" l' what ls c5 ed as n w an; esire d a bt g otected by Letters Patent is set forth in the appended claims:

1. An axial piston machine, comprising a housing defining an elongated interior .chamber having a longitudinal axis and an inner circumferential wall surface; a cylinder block mounted for rotation in said chamber and having two axial ends and a plurality of open-ended passages at least substantially paralleling said axis; a tilt platein said chamber adjacent one of said ends and having a surface inclined to said axis and facing said one end; a plurality of pistons respectively reciprocably received in said passages and each having a free endportion bearing upon said surface and slidable thereon during rotation of said cylinder block; a stationary valve plate mounted in said chamber in sliding contact with the other of said ends, said valve plate having a peripheral margin provided with a circumferential edge face facing but out of contact with said wall surface and a plurality of apertures adapted for registry with said bores of the rotating cylinder block; and at least one circumferential recess in said edge face extending inwardly to the proximity of said apertures but terminating short of the latter, whereby said margin is capable of elastically yielding under stress.

2. A machine as defined in claim 1 wherein said recess is an annular groove having side faces which are spaced longitudinally of said axis and extend in parallelism with one another.

3. A machine as defined in claim 1, wherein said recess is an annular groove having side faces which converge inwardly towards one another.

4. A machine as defined in claim 1, wherein said recess is an annular groove having side faces which are inclined with reference to one another.

5. A machine as defined in claim 1; and further comprising at least one additional circumferential recess provided in said edge face and also extending inwardly towards but short of said apertures.

6. A machine as defined in claim 5, wherein said recesses are of identical cross-sectional outlines.

7. A machine as defined in claim 5, wherein said recesses are of different cross-sectional outlines.

8. A machine as defined in claim 1, said chamber having an open end in the region of said one end of said cylinder block; and further comprising a cover closing said open end and having an inner face directed towards said one end of said cylinder block and supporting said tilt plate thereon.

9. A machine as defined in claim 1, said chamber having an opening in the region of said other end of said cylinder block; and further comprising a closure element closing said opening and contacting said valve plate supporting the same.

10. A machine as defined in claim 1; and further comprising drive shaft means coupled with said cylinder block and operative for rotating the same and for thereby effecting concomitant reciprocation of said pistons. 

1. An axial piston machine, comprising a housing defining an elongated interior chamber having a longitudinal axis and an inner circumferential wall surface; a cylinder block mounted for rotation in said chamber and having two axial ends and a plurality of open-ended passages at least substantially paralleling said axis; a tilt plate in said chamber adjacent one of said ends and having a surface inclined to said axis and facing said one end; a plurality of pistons respectively reCiprocably received in said passages and each having a free end-portion bearing upon said surface and slidable thereon during rotation of said cylinder block; a stationary valve plate mounted in said chamber in sliding contact with the other of said ends, said valve plate having a peripheral margin provided with a circumferential edge face facing but out of contact with said wall surface and a plurality of apertures adapted for registry with said bores of the rotating cylinder block; and at least one circumferential recess in said edge face extending inwardly to the proximity of said apertures but terminating short of the latter, whereby said margin is capable of elastically yielding under stress.
 2. A machine as defined in claim 1 wherein said recess is an annular groove having side faces which are spaced longitudinally of said axis and extend in parallelism with one another.
 3. A machine as defined in claim 1, wherein said recess is an annular groove having side faces which converge inwardly towards one another.
 4. A machine as defined in claim 1, wherein said recess is an annular groove having side faces which are inclined with reference to one another.
 5. A machine as defined in claim 1; and further comprising at least one additional circumferential recess provided in said edge face and also extending inwardly towards but short of said apertures.
 6. A machine as defined in claim 5, wherein said recesses are of identical cross-sectional outlines.
 7. A machine as defined in claim 5, wherein said recesses are of different cross-sectional outlines.
 8. A machine as defined in claim 1, said chamber having an open end in the region of said one end of said cylinder block; and further comprising a cover closing said open end and having an inner face directed towards said one end of said cylinder block and supporting said tilt plate thereon.
 9. A machine as defined in claim 1, said chamber having an opening in the region of said other end of said cylinder block; and further comprising a closure element closing said opening and contacting said valve plate supporting the same.
 10. A machine as defined in claim 1; and further comprising drive shaft means coupled with said cylinder block and operative for rotating the same and for thereby effecting concomitant reciprocation of said pistons. 